1. Field of the Invention
This invention relates to voltage regulators and in particular to ferroresonant type voltage regulators. It is specifically concerned with a voltage regulation technique utilizing voltage waveform control.
2. Prior Art
Prior art regulator circuits regulate voltage by controlling the average value of a transmitted waveform or by controlling the volt seconds integral of a transmitted waveform. Conventional series type and switching type voltage regulators operate by controlling the average value of the transmitted voltage waveform. A series type regulator inserts a variable impedance between the source and the load to control the average value. A switching type regulator pulse width modulates the voltage signal transmitted to the load in order to control the average value.
Ferroresonant type voltage regulators, in contrast to averaging, conventionally regulate the output voltage by controlling the volt seconds integral of a transmitted voltage waveform. A source voltage waveform is applied to a saturating transformer which saturates it at a predetermined volt seconds integral of the applied voltage waveform. The output waveform is limited to the volt seconds integral determined by the saturation of the transformer. This volt seconds limited waveform is then rectified to produce a regulated DC voltage signal.
The ferroresonant regulator has the advantages of being efficient, simple, and reliable. Its major disadvantage is that the output voltage varies directly with the frequency of the input signal to the ferroresonant transformer and, hence, precise regulation is dependent upon the maintenance of the precise frequency of an input signal. This frequency sensitivity problem has been substantially overcome with the development of the feedback controlled ferroresonant voltage regulator which uses an electronic switching device to bring about simulated saturation in the transformer core. This feedback controlled ferroresonant regulator operates to simulate a saturating core when a particular volt seconds value of a waveform has been transmitted through the transformer. This feedback controlled ferroresonant regulator has the capability to regulate for frequency changes.
A typical regulator of this type is disclosed in patent No. RE. 27,916, issued to R. J. Kakalec on Feb. 12, 1974, and entitled "Closed Loop Ferroresonant Voltage Regulator Which Simulates Core Saturation." The feedback controlled ferroresonant regulator, however, in terms of concept of operation, is still a volt seconds integral type voltage regulator as is the conventional ferroresonant regulator.